Field of the Invention
The present invention relates to a controller for cylinder injection type injectors in fuel injection systems for cylinder injection type gasoline engines, or fuel injection systems for diesel engines. More particularly, the present invention relates to a controller for cylinder injection type injectors capable of reducing heat, and reducing the scale of circuits, the size of the controller and hence the production cost of the controller by improving a method of detecting currents flowing through injector coils constituting the injectors.
FIG. 4 is a diagram showing the construction of an exemplary conventional controller for cylinder injection type injectors disclosed in Japanese Patent Application No. Hei 10-165132.
In FIG. 4, various types of sensors 1 for detecting the operating states of an internal combustion engine are provided. Information about the operating states to be detected by these sensors includes, e.g., the throttle opening, intake air amount, engine r.p.m. and engine coolant water.
Control parameter calculation means 2 is constructed of a microcomputer for calculating control parameters, such as fuel injection amount and fuel injection period for supplying a fuel to each cylinder of the internal combustion engine, based on the detection results obtained by the sensors 1 for detecting the operating states of the internal combustion engine. The means 2 outputs, to a controller 4 for cylinder injection type injectors, control signals Cl to Cn for driving the cylinder injection type injectors, respectively, in correspondent with the cylinders of the internal combustion engine. A battery 3 serving as the power source for a vehicle supplies a battery voltage VB.
High voltage generation means 5 for generating high voltage based on the voltage value VB of the battery 3 is provided within the controller 4 for the cylinder injection type injectors. The means 5 generates a high voltage VH by boosting the voltage value VB supplied by the battery 3.
Injector coils 6-1 to 6-n correspond to drive circuits 7-1 to 7-n, respectively. The injector coils 6-1 to 6-n constitute first to nth cylinder injection type injectors. The injectors, respectively arranged for the cylinders of the internal combustion engine, directly inject the fuel into the corresponding cylinders. The drive circuits 7-1 to 7-n supply currents J1 to Jn to the injector coils 6-1 to 6-n as fuel injection signals.
The injector coil drive circuits 7-1 to 7-n arranged so as to correspond to the injector coils 6-1 to 6-n supply the currents J1 to Jn, which are the fuel injection signals, to the injector coils 6-1 to 6-n, respectively, based on the control signals C1 to Cn outputted from the control parameter calculation means 2.
Over-excitation signal generation means 8-1 to 8-n synchronize with the ON timings of the control signals C1 to Cn outputted from the control parameter calculation means 2, and define predetermined time intervals during which over-excitation currents necessary for initially opening the valves of the nozzles of the cylinder injection type injectors rapidly are supplied to the injector coils 6-1 to 6-n from the high voltage generation means 5 through first switching means 9-1 to 9-n, respectively. The means 8-1 to 8-n output the defined time intervals as over-excitation signals E1 to En.
The first switching means 9-1 to 9-n remain turned on while the over-excitation signals E1 to En outputted from the overexcitation signal generation means 8-1 to 8-n are held at the ON state, and hence the means 9-1 to 9-n allow the over-excitation currents to be supplied to the injector coils 6-1 to 6-n from the high voltage generation means 5.
Chopping type holding current generation means 10-1 to 10-n supply, to the injector coils 6-1 to 6-n, holding currents necessary for the injectors to hold the valves of their nozzles open operation while the control signals C1 to Cn outputted from the control parameter calculation means 2 are held at the ON state (after the over-excitation time has elapsed). That is, the chopping type holding current generation means 10-1 to 10-n compare voltage values VS1 to VSn, which are the detection results obtained by current detection means 13-1 to 13-n, with holding current reference voltage values set by themselves, and intermittently supply the battery voltage VB to the injector coils 6-1 to 6-n by controlling the ON/OFF switching operations of second switching means 11-1 to 11-n so that the holding currents are always constant.
The second switching means 11-1 to 11-n start and stop the supply of the voltage value VB from the battery 3 in accordance with the outputs of the chopping type holding current generation means 10-1 to 10-n.
Third switching means 12-1 to 12-n incorporate high-speed current breaking function for rapidly turning off the current when breaking the currents flowing through the injector coils 6-1 to 6-n. The means 12-1 to 12-n are normally turned on, and get turned off upon removal of the control signals C1 to Cn. The means 12-1 to 12-n also have the function of rapidly breaking the currents generated by induced counter-electromotive forces generated at the injector coils 6-1 to 6-n.
The current detection means 13-1 to 13-n detect the currents flowing through the injector coils 6-1 to 6-n. Each current detection means includes, e.g., a current-to-voltage conversion shunt resistor and a differential amplifier connected across both ends of the shunt resistor. The means 13-1 to 13-n are interposed between the third switching means 12-1 to 12-n and the ground, and detect all the currents (over-excitation currents and holding currents) flowing through the injector coils 6-1 to 6-n. Their detection results, which are the voltage values VS1 to VSn, are inputted to the chopping type holding current generation means 10-1 to 10-n and over-current detection means 14-1 to 14-n.
The over-current detection means 14-1 to 14-n detect excessively large currents flowing through the injector coils 6-1 to 6-n based on the voltage values VS1 to VSn corresponding to the currents detected by the current detection means 13-1 to 13-n, i.e., the means 14-1 to 14-n detect the fact that the values VS1 to VSn have grown larger than the reference values within the normal control range. The means 14-1 to 14-n then output voltage values F1 to Fn.
When the over-current detection means 14-1 to 14-n detect the excessively large currents flowing through the injector coils 6-1 to 6-n, failure determination holding means 15-1 to 15-n determine that the injectors for the cylinders have failed, and change the third switching means 12-1 to 12-n from the ON state to the OFF state, thereby rapidly breaking the currents flowing through the injector coils 6-1 to 6-n, and at the same time, output signals H1 to Hn for controlling the third switching means 12-1 to 12-n in order to continuously hold the third switching means 12-1 to 12-n at the OFF states during the operation period.
Diodes D1 to Dn are inserted between the second switching means 11-1 to 11-n and the injector coils 6-1 to 6-n, and are reverse current blocking diodes for blocking the flow of the over-excitation currents supplied from the high voltage generation means 5 via the first switching means 9-1 to 9-n into the second switching means 11-1 to 11-n.
Current commutation diodes D11 to Dnn constitute commutating current paths for allowing currents flowing through the injector coils 6-1 to 6-n to continuously flow while the second switching means 11-1 to 11-n are turned off. The currents commutate through the following paths: from the injector coils 6-1 to 6n, to the third switching means 12-1 to 12-n, then to the current detection means 13-1 to 13-n, then to the current commutation diodes D11 to Dnn, and back to the injector coils 6-1 to 6-n.
By the way, the conventional controller for the cylinder injection type injectors supplies the over-excitation currents necessary for initially opening the valves of the injector nozzles from the high voltage generation means via the paths constituted by the first switching means, the injector coils, the third switching means, the current detection means and the circuit ground in the stated order. After the valves of the injector nozzles have been opened, the holding currents necessary for holding the valves open operation are supplied by causing the chopping type holding current generation means to turn the second switching means on and off, based on the detection results obtained by the current detection means, from the battery via the paths constituted by the second switching means, the reverse current blocking diodes, the injector coils, the third switching means, the current detection means and the circuit ground in the stated order, as well as via the paths constituted by the injector coils, the third switching means, the current detection means and the current commutation diodes in the stated order. However, since the current detection means admit the flow of all the currents supplied to the injector coils (the over-excitation currents and the holding currents) as described above, the current detection means need to have a large allowable power dissipation in order to allow heat derived from these currents.
Further, the detection results obtained by the current detection means are also inputted to the over-current detection means, and hence the current detection means also have the function of disenergizing the third switching means corresponding to the injector coils for the cylinders suffering from over-currents by detecting the over-currents flowing through the injector coils. Therefore, to operate the thus constructed conventional controller properly, the over-excitation currents necessary for initially opening the valves of the injector nozzles should not be detected for abnormal over-currents, and hence the function of the over-current detection means in the conventional controller needs to be temporarily interrupted based on the signals of the over-excitation signal generation means.
Therefore, the conventional controller for cylinder injection type injectors uses large parts for constructing the current detection means with a large allowable power dissipation, and also needs the circuits for temporarily interrupting the function of the over-current detection means, and hence the circuit scale of the controller as a whole is increased. As a result, there arise problems in that the controller itself becomes large in structure in order to provide a capacity large enough to accommodate large circuits therein and a surface area large enough to suppress heat, and hence the production cost of the controller is elevated.